The effects of hyperthermia, ultrasound and microwave treatment of tumor cells on different parameters of the immune response will be evaluated using a syngeneic hamster tumor system. The effects of heating and different heating modalities on the immunological properties of tumor cells deserve further attention. Research in this area could lead to the development of techniques which render tumor cells more immunogenic and/or antigenic, perhaps resulting in enhancement of tumor rejection mechanisms. The proposed work will include: 1. in vitro experiments which will result in a quantitative description of changes in sensitivity of tumor cells to immune lysis following treatment, and 2. in vivo tests to determine the immunological effects of treatment of growing tumors by hyperthermia induced by ultrasound or microwave radiation. Immunological reactivity in vitro will be correlated with observed tumor regressions in vivo. Sensitive assays to quantitate immune responses to tumor antigens are available in our laboratory and are discussed herein.